A possible role of sexuality in the population structure of Diaporthe adunca, a pathogen of Plantago lanceolata

Abstract

In this study, the population structure of the fungal pathogen Diaporthe adunca on its perennial wild host plant Plantago lanceolata was analysed, together with the occurrence of the sexual stage of the fungus. The fungus overwinters on scapes infected in the previous year. In spring, it sporulates asexually on these scapes leading to primary infection sources for an epidemic. From mid‐June onwards, after asexual reproduction has ceased, the sexual stage is formed on the same overwintered scapes. In one location where the sexual stage was prominent, a more diverse fungal population structure was found than in another location where the sexual stage was less frequent and where one clone (with a low female fertility) dominated the same area during three consecutive years. A trade‐off was found between the sexual and asexual reproduction. Female sterile isolates, which have lost the ability to produce the sexual stage, may invest all available nutrients in the scape for asexual reproduction and, therefore, might be selected for under relatively stable regimes. In unstable situations, where there is a lower probability of host plant survival, selection may favour sexual reproduction.